2.From a command prompt with administrative rights, change the directory to the adprep folder on C:

3.If this is 32 bit type adprep32 /forestprep

4.If it is a 64 bit type adprep /forestprep

5.If you plan to add a read-only domain controller (RODC) to the forest, you can run adprep /rodcprep right after you run adprep /forestprep and then verify that both operations have replicated throughout the forest. Both commands require Enterprise Admin credentials; therefore, you might prefer to run them consecutively. If not, you can run the below command next.

6.Once it is complete type adprep32 /domainprep /gpprep

7.Allow the operation to complete, and then allow the changes to replicate throughout the forest before you install a domain controller that runs Windows Server 2008 or Windows Server 2008 R2.

Sounds like you only have one server that you want to upgrade. It looks like you've already got the instructions to do this. I would just add that you should also image the server before going though with the actual upgrade. And if it's a domain controller, taking it off the network while you perform the upgrade wouldn't hurt.